Deck 9: Principles for Competitive-Binding Assays

Question 1

In ____________ competitive-binding assays, paramagnetic particles are used to capture and concentrate bound label on the surface of an electrode.

A)luminescent oxygen channeling
B)microparticle-based light-scattering
C)enzyme multiplied
D)electrochemiluminescent

Answer 1

electrochemiluminescent

Question 2

Which of the following are the two most important characteristics of the fluorophore utilized as the label in fluorescence immunoassays?

A)the wavelength of light absorption and the molecular weight of the fluorophore
B)the extinction coefficient and the magnitude of the Stokes shift
C)the wavelength of light emission and the chemical reactivity of the fluorophore
D)the specificity of the immunoglobulin for the fluorophore and the heterogeneous nature of the immunoassay

Answer 2

the extinction coefficient and the magnitude of the Stokes shift

Question 3

_______ measures the decrease of incident light transmission as a function of light scatter as the size of the aggregated particles increase, and the use of a ________ detection system increases the analytical sensitivity of these measurements.

A)Nephelometry, coupled enzymatic
B)A competitive-binding assay, nephelometric
C)Turbidity, near-infrared spectrophotometric
D)Turbidity, UV/Visible spectrophotometric

Answer 3

Turbidity, near-infrared spectrophotometric

Question 4

In the EMIT system, the absorbance of the product is ______ proportional to the concentration of the unlabeled ligand in the reaction.In the FPIA system, the amount of polarized fluorescent light produced by the reaction is ______ proportional to the concentration of the unlabeled ligand in the reaction.

A)directly, directly
B)directly, inversely
C)inversely, inversely
D)inversely, directly

Question 5

As a preliminary step before performing the assay, some competitive-binding assays either adjust the pH of the patient sample or add an excess of a ligand that is similar to that being measured.Which of the following correctly describes the purpose for these preliminary steps?

A)to release ligands that are bound by endogenous proteins prior to analysis to allow measurement of the total ligand concentration
B)to stabilize ligands that are bound by endogenous proteins prior to analysis in order to prevent these ligands from interfering with free-ligand concentration measurement
C)to release ligands that are bound by endogenous proteins prior to analysis in order to remove these ligands and prevent interference with the concentration measured
D)to stabilize ligands that are bound by endogenous proteins prior to analysis in order to specifically measure the concentration of bound ligand only

Question 6

In competitive-binding assays, the relationship between concentration of unlabeled ligand and percent labeled ligand bound can be described in which of the following ways?

A)logarithmic and direct
B)linear and direct
C)logarithmic and inverse
D)linear and inverse

Question 7

In a competitive-binding heterogeneous assay, the captive phase involves:

A)the removal of endogenous binding proteins that interfere with the immunoassay
B)the binding of the labeled reactant in the assay
C)the capture of free, unlabeled ligands from the patient sample for use in the assay of free ligand alone
D)the initial step in the assay where the antibody binds with the ligand

Question 8

The advantage of using europium chelates, as compared to fluorescein, in time-resolved fluorescence competitive-binding assays is:

A)the stability of the europium-chelate complex
B)the ease of the complexation of europium with ligands and antibodies
C)the magnitude of fluorescence produced by europium chelates
D)the fluorescence lifetime of europium chelates

Question 9

In the fluorescence polarization immunoassay (FPIA) technique, the amount of polarized fluorescent light detected when the fluorophore is excited with polarized light is higher for:

A)low-molecular-weight fluorescence-labeled ligands not bound to antibody
B)low-molecular-weight non-labeled ligands not bound to antibody
C)low-molecular-weight fluorescence-labeled ligands bound to antibody
D)low-molecular-weight non-labeled ligands bound to antibody

Question 10

Which of the following labels is attached to the ligand in the EMIT system?

A)a lanthanide metal such as europium
B)an enzyme
C)the antibody to the ligand
D)a chromophore or fluorophore

Question 11

Which of the following data-reduction methods would convert a curved relationship for competitive protein-binding, dose-response relationships to a linear relationship?

A)Take the inverse of the dosage data, and replot the graph.
B)Take the inverse of the response data, and replot the graph.
C)Take the logarithm of the dosage data, and replot the graph.
D)Change the axes on which the dosage data and the response data are plotted.

Question 12

In microparticle-based light-scattering inhibition immunoassays, as concentration of measured ligand in the patient sample increases, the amount of light scattered in nephelometric measurements ______, and the absorbance reading in turbidimetric measurements ______.

A)increases, increases
B)increases, decreases
C)decreases, decreases
D)decreases, increases

Question 13

All of the following are important aspects of competitive-binding assays except:

A)There must be non-covalent and reversible binding of the antigen to the antibody.
B)The antigenic determinant of the labeled antigen must not be altered by the addition of the label.
C)There must be a limited number of binding sites on the antibody used in the assay.
D)The antigen being measured must be large enough to provoke an immune response.

Question 14

Which of the following approaches to competitive-binding immunoassays would be most likely to improve the sensitivity of the assay for a specific ligand?

A)Simultaneously add the labeled and unlabeled ligand to the reaction mixture containing the appropriate antibody; measure bound labeled ligand after a fixed period of time.
B)Add the unlabeled ligand to the reaction mixture containing the appropriate antibody; allow reaction time; add the labeled ligand and allow a second reaction time; measure the bound labeled ligand
C)Add the labeled ligand to the reaction mixture containing the appropriate antibody; allow reaction time; add the unlabeled ligand and allow a second reaction time; measure the bound labeled ligand.
D)None of the above; the order of addition of the labeled ligand, the unlabeled ligand, and the antibody will have no influence on the sensitivity of the assay.

Question 15

What is the purpose of the "label" used in competitive-binding assays?

A)to aid the technologist in knowing which reagents have been added to the assay
B)to aid the technologist in knowing which patient samples have been added to the assay
C)to aid in assay detection and quantification
D)to aid in the identification of free ligand and ligand bound to endogenous protein

Question 16

Competitive-binding assays that require the antibody-bound, labeled ligand be physically separated from the free labeled ligand are called ________ techniques.Those techniques that do not require physical separation are called _______ techniques, and these assays require _______.

A)homogeneous, heterogeneous, more complex immunochemical reactions
B)heterogeneous, homogeneous, more complex immunochemical reactions
C)homogeneous, heterogeneous, detection by immunonephelometry
D)heterogeneous, homogeneous, detection by immunonephelometry

Question 17

Which of the following best describes the effect of nonspecific binding on the detection limit of an immunoassay?

A)Nonspecific binding will raise the detection limit by lowering the signal-to-noise ratio.
B)Nonspecific binding will lower the detection limit by increasing the signal-to-noise ratio.
C)Nonspecific binding will lower the detection limit by lowering the signal-to-noise ratio.
D)Nonspecific binding will raise the detection limit by increasing the signal-to-noise ratio.

Question 18

ELISA is considered a ______ assay, and EMIT is considered a ______ assay.______ assay would be considered more suitable for automated chemistry analyzers.

A)homogeneous, heterogeneous, homogeneous
B)homogeneous, heterogeneous, heterogeneous
C)heterogeneous, homogeneous, heterogeneous
D)heterogeneous, homogeneous, homogeneous

Question 19

Suppose your laboratory uses the ELISA configuration in which the antibody has been immobilized onto the solid phase.How would the result of the assay for a patient whose specimen is in a specific well be affected by improperly washing the solid phase of that particular well?

A)The patient's result would be falsely elevated.
B)The patient's result would be falsely decreased.
C)The patient's result would not be affected.
D)The impact varies by patient sample and cannot be anticipated.

Question 20

The use of avidin-biotin systems in ELISA serve to:

A)improve the time requirements of the assay
B)overcome diminished antibody capturing capacity in the assay
C)improve the fluorogenic nature of the assay
D)overcome the need for sample extraction prior to performing the assay